Krüppel-Like Factor 4 Promotes Pancreatic Acinar-to-Ductal Metaplasia and Tumor Initiation

Loss of GATA6-mediated up-regulation of UTX promotes pancreatic tumorigenesis and progression

Ubiquitously transcribed tetratricopeptide repeat on chromosome X (UTX), also known as lysine (K)-specific demethylase 6A (KDM6A), functions as a tumor suppressor gene or oncogene depending on the tumor type and context. However, its tumor-suppressive mechanisms remain largely unknown. Here, we investigated the clinical significance and biological effects of UTX expression in pancreatic ductal adenocarcinoma (PDA) and determined the potential mechanisms of its dysregulation. UTX expression and its association with clinicopathologic characteristics of PDA patients were analyzed using immunohistochemistry. UTX mRNA and protein expression and their regulation in PDA cell lines were measured using quantitative polymerase chain reaction and Western blot analyses. The biological functions of UTX in PDA cell growth, migration, and invasion were determined using gain- and loss-of-function assays with both in vitro and in vivo animal models. UTX expression was reduced in human PDA cell lines and specimens. Low UTX expression was associated with poor differentiation and prognosis in PDA. Forced UTX expression inhibited PDA proliferation, migration, and invasion in vitro and PDA growth and metastasis in vivo, whereas knockdown of UTX expression did the opposite. Mechanistically, UTX expression was trans-activated by GATA6 activation. GATA6-mediated PDA progression could be blocked, at least partially, by silencing UTX expression. In conclusion, loss of GATA6-mediated UTX expression was evident in human PDA and restored UTX expression suppressed PDA growth and metastasis. Thus, UTX is a tumor suppressor in PDA and may serve as a prognostic biomarker and therapeutic target.

Pancreatitis initiated pancreatic ductal adenocarcinoma: Pathophysiology explaining clinical evidence

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant lethal disease due to its asymptomatic at its early lesion of the disease and drug resistance. Target therapy associated with molecular pathways so far seems not to produce reasonable outcomes. Understanding of the molecular mechanisms underlying inflammation-initiated tumorigenesis may be helpful for development of an effective therapy of the disease. A line of studies showed that pancreatic tumorigenesis was resulted from pancreatitis, which was caused synergistically by various pancreatic cells. This review focuses on those players and their possible clinic implications, such as exocrine acinar cells, ductal cells, and various stromal cells, including pancreatic stellate cells (PSCs), macrophages, lymphocytes, neutrophils, mast cells, adipocytes and endothelial cells, working together with each other in an inflammation-mediated microenvironment governed by a myriad of cellular signaling networks towards PDAC.

Cancer-associated acinar-to-ductal metaplasia within the invasive front of pancreatic cancer contributes to local invasion

The pancreas is an organ prone to inflammation, fibrosis, and atrophy because of an abundance of acinar cells that produce digestive enzymes. A characteristic of pancreatic cancer is the presence of desmoplasia, inflammatory cell infiltration, and cancer-associated acinar atrophy (CAA) within the invasive front. CAA is characterized by a high frequency of small ducts and resembles acinar-to-ductal metaplasia (ADM). However, the clinical significance of changes in acinar morphology, such as ADM with acinar atrophy, within the tumor microenvironment remains unclear. Here, we find that ADM within the invasive front of tumors is associated with cell invasion and desmoplasia in an orthotopic mouse model of pancreatic cancer. An analysis of resected human tumors revealed that regions of cancer-associated ADM were positive for TGFα, and that this TGFα expression was associated with primary tumor size and shorter survival times. Gene expression analysis identified distinct phenotypic profiles for cancer-associated ADM, sporadic ADM and chronic pancreatitis ADM. These findings suggest that the mechanisms driving ADM differ according to the specific tissue microenvironment and that cancer-associated ADM and acinar atrophy contribute to tumor cell invasion of the local pancreatic parenchyma.

Paracrine Secretion of Transforming Growth Factor β by Ductal Cells Promotes Acinar-to-Ductal Metaplasia in Cultured Human Exocrine Pancreas Tissues

OBJECTIVE

We aimed to evaluate the contribution of acinar-to-ductal metaplasia (ADM) to the accumulation of cells with a ductal phenotype in cultured human exocrine pancreatic tissues and reveal the underlying mechanism.

METHODS

We sorted and cultured viable cell populations in human exocrine pancreatic tissues with a flow cytometry-based lineage tracing method to evaluate possible mechanisms of ADM. Cell surface markers, gene expression pattern, and sphere formation assay were used to examine ADM.

RESULTS

A large proportion of acinar cells gained CD133 expression during the 2-dimensional culture and showed down-regulation of acinar markers and up-regulation of ductal markers, assuming an ADM phenotype. In a serum-free culture condition, ADM induction was mainly dependent on transforming growth factor β (TGF-β) secreted from cultured ductal cells. Human acinar cells when cultured alone for a week in a serum-free condition do not undergo ADM. However, serum may contain other factors besides TGF-β to induce ADM in human acinar cells. In addition, we found that TGF-β cannot induce ADM of murine acinar cells.

CONCLUSIONS

Ductal cells are the major source of TGF-β that induces ADM in cultured human exocrine pancreatic tissues. This culture system might be a useful model to investigate the mechanism of ADM in human cells.